1. Field
The present invention relates to a battery management system, a battery management method, and a power storage apparatus using the same. More particularly, the present invention relates to a battery management system, a battery management method, and a power storage apparatus using the same for quickly performing cell balancing.
2. Description of the Related Technology
Recently, the European Union has decided upon a plan to increase the percentage of renewable energy used to 20% of all energy produced by the year 2020 and to 50% by the year 2050. The U.S.A. is also planning to carry out Renewable Portfolio Standards (RPS). Where renewable energy increases from less than 5% today to up to 30 to 40% in the future, power systems must be prepared for the change.
It is not easy to control the percentage of renewable energy produced. This is because the amount of renewable energy generated changes according to natural conditions, such as solar light, wind power, and wave power. Research is being done on a scheme that is capable of overcoming degradation in power quality and quantity in a power generation system and overcoming the mismatch between production and consumption times. Quality is evaluated on the basis of voltage and frequency. If the supply quantity of renewable energy does not coincide with the demand quantity of renewable energy in real time, abnormalities are generated in voltage and frequency, thereby potentially deteriorating the power quality of all power systems.
A power storage system that is capable of managing such shift in renewable energy is needed. This is because the power storage system can efficiently react to demand and supply by charging electricity when the amount of generation of renewable energy is high and discharging electricity when the consumption of renewable energy is high.
Power storage techniques include pumped power storage, compressed air energy storage (CAES), a flywheel technique, superconducting magnetic energy storage (SMES), rechargeable battery storage, and so on. The pumped power storage technique is a method of storing energy by pumping water up into a dam when excess electricity is available. The water is released from the dam through turbines when the amount of electricity is insufficient. The CAES technique is a method of generating electricity by compressing air in the ground or sea and then discharging the air as occasion demands. The flywheel technique is a method of generating electricity by rotating a flywheel when excess electricity is available and rotating a power generator using the flywheel when electricity is insufficient. The SMES technique is a method using a principle that current stored in a superconducting coil having resistance of 0. The rechargeable battery is a battery that can be repeatedly charged and discharged, and has been used as an uninterruptible power supply (UPS) for temporarily supplying electricity upon a power failure. The rechargeable battery has been used as an auxiliary power source of renewable energy.
The power storage system not only stores the generated power of a renewable energy source to a large capacity rechargeable battery (hereinafter referred to as a battery) of which a plurality of rechargeable batteries are connected to each other, but is also used in cooperation with a grid to store the power of the grid to the battery, or may supply the power stored in the battery to the grid or the generated power of the renewable energy source to the grid.
A battery outputting a high voltage and a large current includes a plurality of rechargeable batteries (hereinafter referred to as cells that are coupled in series. When a plurality of cells are coupled in series, cell balancing for controlling the voltage of each cell may be performed to maintain a voltage difference between the cells within a specified range. A cell in which the cell balancing is not performed deteriorates, and as a result, the life-span of the battery is shortened and the output power is decreased.
During cell balancing, the voltage and the current of the plurality of cells are respectively measured, and a cell having a high voltage or a large current is discharged to decrease the voltage difference with the other cells. The cell balancing is quickly performed so that the battery may stably output constant power.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.